Parchment paper and method of making same



Patented Jan. 12, 1937 PABCHMENT PAPER AND METHOD OF MAKING SAME John A.Newman, Edgeley, Pa... asaignor to Paterson Parchment Paper Company,Bristol, Pa.. a corporation of New Jersey No Drawing. Application July'1, 1934, Serial No. 734,201

11 Claims. (CI. 91-88) The invention relates to the production of a webof parchmentized vegetable fiber which is waterproof and resistant todialysis, capable of retarding evaporation of moisture from articleswrapped therein and possessing a surface which will readily receive andretain printer's ink on either surface.

In the standard vegetable parchment paper on .the market, the vegetablefibres of the paper web are converted by a chemical treatment to agelatinous substance known as amyloid which dissolves as it were orenvelops each individual fibre, completely filling the interstices andby a cementing action bonds the whole into a homogeneous mass. As theresult of the process of parchmentizing the original paper undergoessuch modification that it no longer softens or separates into itsoriginal fibres on being soaked or even boiled in water but retains itscoherence, being impervious to water, and also retains its newlyacquired properties when redried. The conversion is strictly chemicaland the result is a product which is both odorless and tasteless andinsoluble. These qualities render it particularly suitable for manycommercial uses. Although the product is impervious to water, it readilyabsorbs moisture due to the hygroscopicity of the material. Accordingly,although ordinary parchment paper, due to its imperviousness to water,might seem to be an ideal mate-' rial for purposes of wrapping articlesof food or the like, it has not proven itself to be entirelysatisfactory for such uses and it has therefore been a customarypractice in preparing parch- I ment paper for the purpose of serving aswrapping material for moisture-containing products, to place a surfacingcoat of wax or paraffin upon the parchment paper. Due to the solidcharacter of the parchment paper the wax appears as a coating only andis necessarily the product of a wet-wax process, it being impossible todry-wax v the ordinary parchment paper. A sheet of wetwaxed parchmentpaper, .because of its waxed surface, does not readily take on printersink and the amount of wax required is necessarily relatively large.

It is the object of the present invention to pro-- duce a dry-waxedparchment paper which will Confronted with the generalh! accepted factthat vegetable parchment was supposed not to be capable of responding toa dry-wax process, I

conceived the idea that if the parchmentizing treatment were not carriedto the full extent used in making the standard paper, there might be apossibility of establishing in the paper a certain porosity sufllcientto permit the paper to become subject to a dry-wax process and stillretain the advantages of a parchmentized surface. Experiments based onthis idea resulted in the discovery that if in the parchmentizingprocess the period of exposure to the chemicals was shortened or thechemicals were somewhat weakened, or retarded in their action upon theinterior fibres of the paper web, or a combination of any of theseconditions were employed, a product would result which, while possessinga well parchmentized surface, was sufficiently porous or absorbent totake up wax or paraffin in its interior structure between the outerparchmentized surfaces in the interior fibres which had been at best butfeebly parchmentized, leaving the outer surfaces relatively free of wax.

This is accomplished by passing one surface a of the porousparchmentized web over a roll which applies fluid parafiine and thenpassing the web between heated drums under slight compression. The waxedpaper is then wound on a roll and, being quite hot, the roll ispermitted to stand for several hours and in the process of cooling inthe tightly wound state the wax is apparently further driven into thefibrous portions of the web and away from the parchmentized surfaces.

The outer surfaces of the thus dry-waxed parchment paper can be readilyprinted upon and such printing isnot smudged or blurred by reason of thepresence of the wax within the body of the paper. The thickness of thepaper is not materially increased and due to the fact that there is thuscreated a continuous barrier or sheet of wax throughout the entireinterior portions of the parchment, the moisture contained in articleswrapped in such paper will not be transmitted through the paper andwhatever moisture is taken up by the parchmentized portion of the paperon one surface thereof cannot.

readily pass through to the other because of the interposed barrier ordam of wax. The new drywaxed product, to all appearances, is ordinaryparchment paper. It does not possess the feel of waxed paper. Theinterior film of wax is so thin that a paper parchmentized according tothe new method which prior to the parchmentizparchment.

ing treatment weighs 27% pounds per 500 24" x 36" sheets, will take uponly about three pounds of paraflin per ream. In making the newdry-waxed parchment paper the web may, after the completion of theparchmentizing operation, be treated with a softener or plasticizer suchas glycerine for rendering the sheets flexible and pliable and thepresence of the glycerine does not interfere with the capacity of theinterior unparchmentized or feebly parchmentized fibrous section of theproduct from absorbing the paraffin. The new product retains theessential characteristics of vegetable parchment and is useful forwrapping, for box linings, and it retards evaporation or escape ofmoisture as in the case of butter, soap, and other products, andprevents dialysis as is the case of butter containing salt and has manyother advantages readily apparent to many classes of users.

A special advantageous feature of the new product is that it can readilybe attached to other objects or to portions of itself by means of glueor other cementing material without any difficulty such as isexperienced in attempting to glue together waxed paper or wet-waxed Inview of the fact that no injurious ingredients are employed, the papercan be safely used in connection with food stuffs.

The process of manufacturing ordinary vegetable parchment involves theinitialJmanufacture or use of a paper such as water leaf which containsno sizing and is very soft and absorbent, these qualities beingessential for the success of the parchmentizing or chemical step. Theparchmentizing or chemical process consists in subjecting the paper webto the action of chemicals such as sulphuric acid, phosphoric acid, zincchloride, or other agents which will convert the flbresof the paper intoa gelatinous substance. A customary strength of acid is about 55 B.(69.65% H2804 at 60 F.)' to'56" B. (71.17% H2804 at 60 F.) but the rangeis, of course, subject to considerable fluctuation as to acid strengthand temperature. A typical speed at which the paper is'passe'd throughthe acid, for example, in the case of a paper weighing 27 pounds for 50024" x 36" sheets, is about 350 feet per minute. As the thickness of thepaper increases, the run is correspondingly. slower. When theacid-treated paper leaves the acid bath, the adhering acid is washed oifand the paper passes over drying drums and is then finished parchmentpaper.

A typical example of making the new-paper involves a reduction in thestrength of acid to for example 53 B. (65.49% H2804 at 60 F.) with orwithout an increase in the speed of the machine or maintaining the speedconstant, reducing the amount of paper which passes through the bathperunit of time. In any event, the correlation of the factors referredto should be such as to produce a sheet of a porous nature in which alightly parchmentized web is secured whose top and bottom surfaces areboth lightly parchmentizedwhile the interior consists of unparchmentizedor but very feebly parchmentized fibres. Inasmuch as the pulp from whichthe paper is made varies somewhat and some paper is denser or morecompressed than other paper of the same weight, the process will besubject to adjustment from time to time whenever the desired result isnot obtained. These adjustments are very readily made, preferably by acontrol of .the speed of the paper through the .acid and/or the control.of the length of paper immersed at any moment in the acid bath. Controlssuch as these are well understood by those skilled in the art.

In the preferred process the control manipulations just referred to arethe only ones 'employed, while the strength of the acid is allowed toremain the same as that used for making standard parchment paper becausein that event the same acid can be used for all parchmentizingoperations used in the plant including the new process, and for allweights of paper.

Because of the light parchmentization resulting from the new practice, acondition is set up in the product which makes it possible to drivesomething into a sheet which, if it had been subjected to the standardparchmentization paper.

In the new process the desired result may also be obtained withparchmentizing agents other 7 than sulphuric acid such for example asphosphoric acid, zinc chloride, or other chemicals "effecting a similarconversion of vegetable fibres into a parchmentized product. It is alsopossible in connection with the new process to load the raw materialwith pigments, for example, titanium oxide, or opaque pigments, orsizing material for the purpose of retarding the parchmentizing effectof the acids used with the result that acids of the standard or higherconcentrations can be used to obtain the result aimed at.

The wax-filled parchment paper is also capable of being used to producespecial effects by the application of heat and pressure. In case, forinstance, the point of a hot metal instrument is drawn over the sheetunder pressure, the path of the instrument remains visible on the sheetas a transparent track.

It is understood that the invention is not restricted to any particularor prescribed method or process of parchmentizing and is not limited ito any particular or specific form of wax or waxed material, but isdirected broadly to the! production of a dry-waxed parchmentized paperin which dry-waxing has been 'made possible by limiting theparchmentizing effects of the chemicals used in the parchmentizingtreatment, to a condition where the paper is still sufllciently porousto absorb wax-like substances in its interior fibrous structure and theweb has not yet become so completely parchmentized as to be imperviousto access by fluid waxy substances into its interior. I

Furthermore, the impregnating substance need not necessarilybe wax orparaflln but may be a substance such as rubber latex or medicatedmaterial or any other substance which is'absorbable by' theparchmentized web and is capable of remaining in the web up to the timeof the use for which the impregnating substance is selected. For thepurposes of my broader claims any such substances are to be regarded asthe equivalents of wax or paraflln.

When it is stated in some of the claims that one or both surfaces of thepaper are substantially free from wax, it is not intended to indicatethat no wax can be located on such surfaces. The phrase is employed toconvey the thought that while there may be some small amounts of wax onthe surfaces, wax is not present in such amounts as to impart a waxyfeel to the paper, or to prevent the surfaces from being capable ofreceiving and retaining printer's ink, or to prevent ordinary glue fromexerting a strong binding effect when used to join two sheets together.

I claim:

1.'A vegetable parchment paper having relatively light parchmentizedexterior surfaces and.

a fibrous interior section substantially unparchmentized, porous withrespect to the entry into the interior thereof of extraneously appliedwax,

the fibrous interior section being impregnated with a wax, the finishedproduct forming a drywaxed parchmentized paper at least one surface ofwhich is capable of receiving and retaining printers ink.

2. A vegetable parchment web having relatively lightly parchmentized topand bottom sur- 4. A vegetable parchment web having rela-' tively lightparchmentized top and bottom surfaces, an interior fibrous structuresubstantially unparchmentized, and a plasticizer such as glycerindiffused throughout the web, the interior fibrous structure beingimpregnated with wax, at least one'of the surfaces of the paper beingsubstantially free from wax.

5. A vegetable parchment web having relatively light parchmentized topand bottom surfaces, an interior fibrous structure substantiallyunparchmentized, and ,a retarder of parchmentizing effects such aspigments or sizing described throughout the web, the interior fibrousstructure being impregnated with a wax, at least one surface of thepaper .being substantially free from wax.

6. A vegetable parchment web having relatively lightly parchmentized topand bottom surfaces and an interior fibrous structure substantiallyunparchmentized, the latter being impregnated with paraflin, at leastone of the surfaces of said Web being free from paraffin.

. '7. The process of producing vegetable. parchment paper which consistsin passing a porous paper web through an acid bath to causeparchmentization of the exterior surfaces of the. web, removing the acidand drying, and in the parchmentizing treatment limiting the extent ofparchmentization so that the same shall effect an activeparchmentization of the surface portions of the web but shall notproceed beyond the stage where the web, when subsequently washed anddried, is no longer sufficiently porous to absorb in its interior wax orparafiin applied by a dry-wax process, and impregnating the interiorstructure of said web with a wax by a dry-waxing process.

8. A method of making dry-waxed paraflin paper which comprises passing aporous paper web through an acid bath, regulating the effect of the saidaction onthe web to limit the treatment to a light parchmentization,leaving the web porous'and its interior still fibrous and substantiallyunparchmentized, removing the acid,

drying, subjecting the dry porous web to a drywax process, impregnatingthe interior fibrous structure of the web with wax and leaving the outerparchmentized surfaces of the web relatively uncoated, and causing theimpregnated wax to congeal in the-web.

9. The method of making dry-waxed paraffin paper which comprises passinga porous paper web through an acid bath, regulating the effect of thesaid action on the web to limit the treatment to a lightparchmentization leaving the web porous and its interior still fibrousand substantially unparchmentized, removing the acid, drying, bringingthe dried web into contact with a wax by a dry-wax process to impregnatethe fibrous interior of. the web while leaving the surfaces of the webssubstantially free and uncoated, subjecting the resultant product tosimultaneously applied heat and pressure, rolling up the thus treatedweb while still hot into rolls and causing dissipation of the heat fromthe hot web while in the rolled-up condition.

10. The method of making dry-waxed paraffin in the rolled-up condition,whereby the interior structure is impregnated with the wax andv thesurfaces are substantially unaffected.

11. The method of making dry-waxed parafiln paper which comprisespassing a porous paper web through an acid bath, regulating the effectof the said action on the web to limit the treatment of a lightparchmentization, leaving the web porous and its interior still fibrousand substantially unparchmentized, removing the acid, drying, subjectingthe dried porous web to a dry-wax ,process to impregnate the interiorfibrous structure of the web with wax and leaving the outerparchmentized surfaces of the web relatively uncoated, causing the waxto congeal in the web and locally applying heat under pressure to'createpatterns of greater transparency at the localities where said heat andpressure are applied.

JOHN A. NEWMAN.

